Phytotaxa 81 (1): 38–44 (2013) ISSN 1179-3155 (print edition) www.mapress.com/phytotaxa/ Article PHYTOTAXA Copyright © 2013 Magnolia Press ISSN 1179-3163 (online edition) http://dx.doi.org/10.11646/phytotaxa.81.1.11

Validation of the name Pogostemon petelotii (Lamiaceae)

GANG YAO1, 2, YUNFEI DENG1 & XUEJUN GE1 1Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, The Chinese Academy of Science, 510650, Guangzhou, People’s Republic of China. E-mail: [email protected], [email protected] (author for correspondence), [email protected]. 2Graduate University of Chinese Academy of Sciences, 100049, Beijing, People’s Republic of China.

Abstract

Dysophylla petelotii, originally described from Vietnam in 1936, is an invalidly published name because of the lack of a Latin diagnosis. It was later transferred to Pogostemon as P. petelotii (Doan) Phuong and P. petelotii (Doan) Budantzev, but neither Phuong nor Budantzev validly published the name P. petelotii because the basionym had not yet been validly published and neither of them provided a Latin diagnosis. Based on the studies of herbarium material, P. petelotii can be recognized as an independent species. We validate the name through providing an English diagnosis. Pogostemon petelotii is very closely related to P. cruciatus, but can be easily distinguished from the latter by leaf characters.

Key words: nomenclature, taxonomy, Thailand, Vietnam

Introduction

The genus Pogostemon Desfontaines (1815: 154) consists of about eighty species and is distributed mainly in tropical and subtropical Asia with another five species endemic to Africa (Bhatti & Ingrouille 1997, Harley et al. 2004). It belongs to the tribe Pogostemoneae, subfamily Lamioideae of the family Lamiaceae (Harley et al. 2004, Scheen et al. 2010, Bendiksby et al. 2011). The most recent revision of the genus was published by Bhatti & Ingrouille (1997), with 79 species recognized. Bhatti & Ingrouille (1997) re-circumscribed the genus with the reduction of Dysophylla Blume (1826: 826) and divided the genus into three subgenera: P. subgen. Pogostemon, P. subgen. Allopogostemon Bhatti & Ingrouille (1997: 97) and P. subgen. Dysophylla (Blume 1826: 826) Bhatti & Ingrouille (1997: 107). In the Flore Générale de L'Indo-Chine, Doan (1936) described many new taxa of Lamiaceae in French. But according to Art. 39.1 of the ICN (McNeill et al. 2012), these names were not validly published because no Latin diagnoses were provided. A number of invalid new combinations have been made based on Doan's names (e.g., Hara 1985, Phuong 1995, Paton 1997, Budantzev 1999, Chuakul 2002). Suddee and his colleagues validly published most names of Doan except for those names which they did not accept (Suddee et al. 2004a, 2004b, 2005, Suddee & Paton 2006). Dysophylla petelotii Doan (1936: 967) is one of those names published by Doan. Later it was transferred to the genus Pogostemon by Phuong (1995, 2000) and Budantzev (1999), who both made new combinations, Pogostemon petelotii (Doan) Phuong (1995: 44) and Pogostemon petelotii (Doan) Budantzev (1999: 23), respectively. Neither Phuong or Budantzev validated the name Pogostemon petelotii because the basionym had not yet been validly published, and neither of them provided the necessary Latin diagnosis or description when they made the new combination. When they validated some names of Lamiaceae, Suddee & Paton (2006) recognized that either “Dysophylla petelotii” or “Pogostemon petelotii” might be conspecific with Pogostemon cruciatus (Bentham 1830: 30) Kuntze (1891: 530) and thus did not validate the names “Dysophylla petelotii” or “Pogostemon petelotii”.

38 Accepted by Hans-Joachim Esser 8 Feb. 2013; published online in PDF: 19 Feb. 2013 In the course of studying the phylogeny and taxonomy of the genus Pogostemon, we checked the collection Petelot 1300 (Fig. 1 A) cited by Doan under “Dysophylla petelotii”, and concluded that it can be separated from P. cruciatus (Fig. 1 B). Because the taxon was not validly described before, we validate it here, using the epithet “petelotii” originally proposed by Doan (1936), through an English diagnosis as allowed by recent changes of the Code (Art. 39.2 ICN, McNeill et al. 2012; see also Knapp et al. 2011), even though it was first described seventy-five years ago.

Taxonomic treatment

Pogostemon petelotii Doan ex Gang Yao, Y. F. Deng & X. J. Ge, sp. nov.

Diagnosis:—The species is similar to Pogostemon cruciatus (Benth.) Kuntze in habit, but differs from the latter in its stems and leaves being whitish adpressed tomentose, leaf margins not revolute and dentate apically, midrib conspicuously elevated, and lateral veins in 3–5 pairs.

Type:—VIETNAM. Thonh Hoa: Bim-son, anciennes rizieres, December 1923, P. A. Pételot 1300 (holotype P! [sheet no. P00344448]; isotypes P! [sheets nos. P00344449, P00344450]).

Annual herb, to 40 cm tall. Stem terete, unbranched or rarely branched, straight, erect, striate on lower portion, adpressed whitish tomentose with long hairs. Leaves 4–6-verticellate, sessile; blades elliptic-linear, 1–3 cm × 3–7 mm, apex obtuse, margin not revolute, sometimes dentate apically, base rounded or broadly cuneate, tomentose on both surfaces, hairs unicellular, midrib elevated abaxially, lateral veins 3–5 on each side of midrib. Inflorescence terminal, 5–7 cm × 38 mm, densely flowered, not interrupted, tomentose; bracts linear, villose, longer than the calyx, long-hairy; calyx campanulate, 1.5–1.8 mm in length, 4-angled and more or less quadrangular, villose outside, lobes 5, subequal; corolla pinkish, very shortly exserted from the calyx tube, lobes oblong, subequal, pubescent outside, corolla tube about 2 mm in length; stamens 4, about 4 mm in length, inserted at the mid-part of the corolla tube; filament twice as long as the corolla, joined to the middle of the corolla tube, hairy; anther stalks tapered at the base which is pubescent, bearded at the mid part and more than twice as long as the corolla; anther 1-locular, cell apex dehiscent. Ovary glabrous; stigma shortly bifid at apex. Nutlets not seen. Distribution and habitat:—Pogostemon petelotii is found in Thailand and Vietnam. It grows in grassland in open places at elevations of 1000–1300 m. Etymology:—The specific epithet “petelotii” was originally proposed by Doan (1936) for the species to be in honor of French botanist P. A. Pételot (1885–after 1940), who first collected the species in Vietnam. Discussion:—According to the classification of Bhatti & Ingrouille (1997), Pogostemon petelotii belongs to P. subgen. Dysophylla. Obviously, it is closely related to P. cr u c ia t us , but differs from the latter by having the stems and leaves whitish adpressed tomentose (Fig. 1 C), leaf margins rarely revolute and sometimes dentate apically, midrib elevated conspicuously (Fig. 3) and lateral veins in 3–5 pairs (Fig. 1 C). Pogostemon cruciatus has the stems and leaves brown spreadingly hirsute (Fig. 1 D), leaf margin usually revolute and quite entire, midrib inconspicuously elevated (Fig. 1 D) and lateral veins invisible (Fig. 1 D). P. c r u c i a tu s is distributed in India, Nepal, Myanmar, China, Thailand, Vietnam, Laos and Cambodia. Trichomes are widely used in taxomomic studies in the family Lamiaceae (Cantino 1990, Gairola et al. 2009, Xiang et al. 2010, Hu et al. 2012). In Pogostemon, most species have multi-cellular, simple hairs except for two species that have unicellular hairs (Bhatti & Ingrouille 1997). We observed the trichome morphology of leaves of P. petelotii and P. c ru c ia t us under scanning electron microscopy and light microscopy. The results showed that P. petelotii has unicellular hairs (Fig. 3 F) more densely covered on the leaf surfaces (Fig 3 B, D), and P. c ru c ia t us has 2–3-cellular hairs (Fig. 3 E) more sparsely covered on the leaf surfaces (Fig. 3 A, C).

VALIDATION OF THE NAME POGOSTEMON PETELOTII (LAMIACEAE) Phytotaxa 81 (1) © 2013 Magnolia Press • 39 FIGURE 1. A. Holotype of Pogostemon petelotii (Pételot 1300, P); B. Isotype of P. cruciatus (Wallich 1541, K); C. Leaves of P. petelotii (Pételot 1300, P); D. Leaves of P. cruciatus (Wallich 1541, K). Scale bars: C, D = 1 cm. A and C reproduced with permisson by the Muséum National d'Histoire Naturelle (MNHN), Paris; B and D with permission by Herbarium of the Royal Botanic Gardens, Kew (K))

40 • Phytotaxa 81 (1) © 2013 Magnolia Press YAO ET AL. FIGURE 2. Pogostemon petelotii. A. Habit; B. Flower; C. Corolla split with stamens; D. Calyx split with style; E. Stamen; F. Anther; G. Bracts. Based on G. Murata et al. T-42045 (IBSC).

The identification key to distinguish Pogstemon petelotii and P. cr u ci a tu s is provided below.

1a. Stems and leaves whitish adpressed tomentose; hairs on leaves unicellular; leaf margin rarely revolute and some- times dentate apically, midrib conspicuously elevated, and lateral veins in 3–5 pairs; calyx tube 4-angled ...... P. petelotii 1b. Stems and leaves brown spreadingly hirsute; hairs on leaves 2–3-cellular; leaf margin revolute and quite entire; mid- rib inconspicuously elevated, and lateral veins invisible; calyx tube rounded ...... P. cruciatus

VALIDATION OF THE NAME POGOSTEMON PETELOTII (LAMIACEAE) Phytotaxa 81 (1) © 2013 Magnolia Press • 41 Additional specimens examined:—THAILAND. Northeastern: Loei: Phu Kradung, S. of Loei, 16º53’N, 101º53’E, 1100 m, 7 November 1970, C. Charoenphol, K. Larsen & E. Warncke 4610 (AAU, E!); Udawn, Phu Kradung, on the plain at its summit, 1100–1200 m, 28 Novemner 1965, M. Tagawa, K. Iwatsuki & N. Fukuoka T479 (E!); Phu Kradung, 16º52’N, 101º48–50’E, along the trail to the headquarter of National Park, 900–1200 m, 30 October 1984, G. Murata, C. Phengklai, S. Mitsuta, T. Yahara, H. Nagamasu & N. Nanlasan T-42045 (IBSC! [sheet no. 0567266]); Phu Kradung, 1300 m, 29 November 1958, T. Sörensen, K. Larsen & B. Hansen 6313 (KUN! [sheet no. KUN213610).

FIGURE 3. Trichome morphology of leaves under scanning electron microscope and light microscope. Pogostemon cruciatus (G. Forrest 25140, IBSC): A. Trichome on the upper surface; C. Trichome on the lower surface; E. 2–3-cellular trichome. P. petelotii (T. Sörensen et al. 6313, KUN): B. Trichome on the upper surface; D. Trichome on lower surface; F. unicellular trichome. Scale bars: E–F = 0.1 mm.

42 • Phytotaxa 81 (1) © 2013 Magnolia Press YAO ET AL. Acknowledgements

This study was financially supported by Firmenich Aromatic (China) Ltd. Co. as a part of the research project IN-CD-DS-YGY002. The authors are indebted to the curators of herbaria E, IBSC, K, KUN and P for providing images of related specimens or hosting our visits, Ms. Yun-Xiao Liu for the illustrations, and Ms. Xiao-Ying Hu for technical assistance with SEM observation.

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